The invention relates to an apparatus for dehumidifying solids being transported by a flowing gas, in particular plastics granulated under water, by using an elongated pneumatic conveying channel followed by deflecting means provided at its outer wall with a screen. The deflecting means is directed upwardly in the direction of flow.
German Patent Publication (DT-OS) No. 2 231 722 already discloses an apparatus for dehumidifying granulated plastics. With this apparatus moist granulated material as well as compressed air are supplied to the inlet of a horizontal conveying channel. The compressed air serves to transport the moist granulated material in the conveying channel and, at the same time, the liquid adhering to the granulated material is partly torn away from the granulated material. The end of the conveying channel is followed by a deflecting portion which is directed upwardly and the outer wall of which consists of a screen. This deflecting portion changes the flow direction of the granulated material and any liquid still remaining in the granulated material is expelled by centrifugal action. The air which is carrying the moisture leaves through the screen. The velocity imparted to the granulated material by the air is sufficient to convey the granulated material along the deflecting portion until it is discharged at the end of the deflecting portion into a downwardly directed outlet channel. If the dehumidification is insufficient, several of such devices are connected in series behind one another, whereby an outlet channel opens from above into the respective inlet of the next successive conveying channel. Said prior art apparatus or its multiple arrangement requires a relatively large space and particularly high construction expenses because of the individual design of all its structural elements.
Moreover, it is known from German Patent Publication (DT-AS) No. 1 220 793 to convey bulk material downwardly through chutes arranged on top of one another in zig-zag shape and each directed obliquely downwards. The bottom of these chutes is provided with slots to let air enter so that a fluidized bed is formed in the area of the inclined chutes. The air is supplied through an air supply channel disposed below each chute. Upon passing through the slots the air whirls up the bulk material and causes it to flow. Then the air is withdrawn from each chute above the bulk material through a separate air discharge channel. Structurally this means that between two chutes one of which is disposed on top of the other there is positioned an air supply channel as well as an air discharge channel, which makes the structure correspondingly expensive. Furthermore, the known system is not suitable for drying because it does not have any screens in the area of the deflecting portions which connect the ends of the chutes. In the deflecting portions consequently the bulk material merely falls from the upper chute to the one below.